Kenwood L 07M II (c. 1978–1980)
A high-speed DC monaural power amplifier with extreme bandwidth and ultra-low distortion, built for precision audio reproduction.
Overview
The TRIO L-07MII, sold as Kenwood L-07MII in international markets, is a monoblock DC power amplifier introduced around 1978. It was designed for a minimal signal path and maximum stability. It delivers 150 watts into 8 ohms with very low distortion. Compared to the L-07M, it extends the frequency response up to 600 kHz and improves transient performance. The L-08M succeeded it around 1980.
Specifications
| Rated Output (10 Hz to 100 kHz) | 150W (8 Ω) |
| Total harmonic distortion factor at rated output 8 Ω, 10 Hz to 100 kHz | 0.08% |
| Total harmonic distortion factor at rated output 8 Ω, 20 Hz to 20 kHz | 0.007% |
| Total harmonic distortion factor at rated output 8 Ω / 4 Ω, 1 kHz | 0.003%/0.0035% |
| Total harmonic distortion factor at 1/10 rated output 20 Hz to 20 kHz | 0.008% |
| Frequency characteristic | DC ~ 600 kHz +0 dB -3dB |
| Cross modulation distortion factor (60Hz:7kHz=4:1) 8 Ω at rated output | 0.003% |
| Cross modulation distortion factor (60Hz:7kHz=4:1) 8 Ω at 1/10 rated output | 0.002% |
| Output bandwidth | 10 Hz to 100 kHz (IHF Distortion Factor 0.08%) |
| Signal-to-noise ratio (IHF-A) | 120dB |
| Input Sensitivity / Impedance | 1.0V/50k Ω |
| Damping factor Output terminal DC ~ 26kHz 8 Ω / DC ~ 65kHz 8 Ω | 150 / 100 |
| Damping factor 1m Cord Tip DC ~ 20kHz 8 Ω / DC ~ 40kHz 8 Ω | 120 / 100 |
| Transient response Rise Time | 0.55 μs (+1V to -1V, +20V to -20V, +40V to -40V) |
| Transient response Slew Rate | +170 V/μs, -170 V/μs |
| Rated power consumption | 190W |
| Power | 100 V, 50Hz/60Hz |
| Power outlet Power Switch Non-Interlocked | 1 Piece / 300W |
| External dimensions | Width 200 x Height 155 x Depth 390 mm |
| Weight | 13kg |
Design
The L-07MII is a direct-coupled DC amplifier with a minimal signal path from input to output. The voltage amplification stage uses a 3-stage differential front-end with dual FETs for low temperature drift. The current amplification is a two-stage Darlington triple push-pull circuit with EBT (Emitter Ballast Transistor) technology, which puts 300 low-power transistors with emitter resistors on a single chip for stable, high-power output. The power supply is isolated from the signal path and has a large transformer and dual 18,000 μF capacitors. Every stage before the drive stage runs in Class A, fed by a separate high-voltage stabilizing supply. Heat goes out through an aluminum die-cast chimney-type heatsink that cools by convection. The signal path uses high-precision single-metal coating resistors, and specialized low-distortion electrolytic capacitors replace film types where performance is critical. It has a gold-plated screw-lock pin jack and comes with a 1-meter low-capacitance, low-inductance speaker cord. The cord is made of seven twisted pairs with foamed polyethylene insulation.
Context
Market
A tested working single unit was listed for C $610.56 with C $115.04 shipping. Current listings describe it as a rare mono block amplifier.
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